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Volume 8, Issue 2 (Suppl) Chem Sci J 2017
ISSN: 2150-3494 CSJ, an open access journal Euro Chemistry 2017
May 11-13, 2017
May 11-13, 2017 Barcelona, Spain
4th European Chemistry Congress
Pervin Unal Civcir, Chem Sci J 2017, 8:2(Suppl)
Computational study of the synthesis of pyrrole-pyrazines
Pervin Unal Civcir
Ankara University, Turkey
In continuation of our studies of extended heterocyclic systems with potential semi-conductivity and nonlinear optical properties,
we have synthesized and studied theoretically some pyrazine derivatives possessing a pyrrole (or thiophene, or furan) ring systems.
Extension of the Stetter protocol used in the previous work 1-4 was unsuccessful for the pyrazine analogues because of the poor
accessibility of formylpyrazine only gave a complex mixture of products from which the pyrazine could not be isolated.5 We have
tried to obtain pyrrolylpyrazine, furylpyridazines, and thienylpyridines from formylpyridazines, via the Paal-Knorr reaction on
the intermediary pyrazinyl- 1,4-diketones, using ammonium acetate, polyphosphoric acid or Lawesson's reagent 14, respectively
(Scheme 1). The intermediate 1,4-diketone was synthesized via the Stetter reaction in the presence of thiazolium salt as a catalyst.
Therefore, we aimed to study theoretically in detail the mechanism of the synthesis for the pyrazine derivatives. In this work, the
experimentally suggested mechanisms of Stteter6 and Paal-Knorr7,8 reactions for only pyrrolypyrazine have been modelled with
density functional theory (DFT)9, which gives low computational cost and accurate results. Geometries of stationary points along the
reaction coordinate have been optimized at BP3LYP10,11 (the hybrid gradient-corrected exchange functional, proposed by Becke,
combined with the gradient-corrected correlation functional of Lee, Yang, and Parr) levels of theory using 6-31G* and 6-31G** basis
sets12 without any symmetry consideration. Vibrational frequency calculations were used to characterize all stationary points as
either minima (no imaginary frequencies) or transition states (with only one imaginary frequency). Vibrational frequencies were
also used to evaluate zero point energies and the thermodynamic data. Intrinsic reaction coordinate (IRC) calculations were traced
to ensure that the transition states connect the proper minima.13 Mechanisms of the reactions are explained in the potential energy
diagrams.
This study was supported by Ankara University BAP Project Coordinator by code number 12A4240001.
Biography
Civcir completed her PhD at the University of East Anglia, UK in 1992 and became a professor in Ankara University in 2009. She is a lecturer in Ankara University,
Faculty of Science, Chemistry Department. She works in the field of Organic and Computational Chemistry and has published more than15 papers in reputed
journal. She has written a Chemistry book in Turkish. She was involved in translating the five Chemistry books from English to Turkish.
N
N
O
H i
N
N
O
+
O O N
N X
X = NH , O , S
ii , iii , or i v
i : Thi azo li um c hl or id e , t r i e thyl am i ne , di oxane
ii : A mmon i um ace t a t e ,
II : P o lyph os ph or i c ac id
III : L awesson ' s rea g en t